This invention relates to a communication line scanning device provided, for instance, for a communication controller and more particularly, to an address generating device to be used in a scanning device for scanning a variable number of lines on which data are transmitted at different rates.
Communication controllers are provided to be included in data teleprocessing systems, in order to manage the transmissions performed on the various lines connected thereto. In general, the main control of the teleprocessing network is concentrated in one or several central processing units (CPU) containing a directory of the rules applied for processing data issued from or directed to the terminal units or terminals of the teleprocessing network. Sending and receiving data through communication lines are managed by communication controllers depending on the central processing unit(s). But in addition to the execution of actual transmission controls, the controller is also in charge of executing the directory functions, in particular the functions directly relating to the standard transmission procedures. Due to this fact, the central processing units are exempted from carrying out the corresponding tasks and can be used for executing other works.
The communication controller consists in a sophisticated assembly provided with an intelligence mainly concentrated in one or several central control units (CCU). The central control units are connected, on the one hand, to the terminals through line adapters and, on the other hand, to the central processing units through channel adapters so called because they are connected to the channels of the central processing unit(s).
The line adapters can serve a certain number of lines by means of a cyclic scanning device and a random access memory assembly temporarily containing the data received or to be sent on the various lines as controlled by the scanning device.
In such an environment, each line adapter can be connected to a variable number of lines exchanging information with terminals of various types and therefore, the protocols and the transmission rates of the data on these lines, are different. In order to have a data communication network exhibiting a maximum flexibility, it is necessary to use the same scanning device in the line adapters whatever the number of lines to be scanned and whatever protocols and transmission rates are used on these lines.
The scanning device includes a line address generating device allowing the communication lines to be successively addressed to cause the communication controller to receive or to send a bit of the message on each scanning period assigned to the line.
The transmission rate on the various lines is not the same due to fact that the communication controller can manage lines at very high speed or at low speed and the frequency at which the lines should be scanned is not the same for all the lines. Consequently, the line address generating unit should be able to be adapted in function of the configuration of the lines to be scanned.